Abstract
The treadmill test has become an invaluable tool for diagnosing the presence and the extent of coronary artery disease. However, its clinical usefulness in our country has not been clarified because there are few reports describing the exact sensitivity and specificity of the test in Japanese patients, and because many of the patients are unable to accomplish submaximal or maximal exercise.
To evaluate the clinical significance and usefulness of the test, 699 cosecutive graded treadmill tests done on out-patients in our center were analyzed. One hundred and seventy-seven hospitalized patients who underwent both treadmill test and coronary arteri-ography were also analyzed. In the latter group, the patients with previous myocardial infarction were excluded from the study. In addition, in order to evaluate the exact value of treadmill test in the diagnosis of ischemic heart disease due to fixed organic coronary artery lesions, we excluded patients with vasospastic angina. The graded treadmill exercise test was carried out to a symptom-limited or submaximal work load of 90% of an age-related predicted maximum heart rate (MHR), using a computer-assisted-system-for-exercise from Marquette Corporation. Diagnostic ST changes were defined as 1mm or greater ST depression at the J point for horizontal or down-sloping ST depression, and 1.5mm or more ST depression at 80 msec from the J point for up-sloping ST depression (1mm to 1.5mm: equivocal result). Of 699 out-patients, positive, negative, and equivocal test results were obtained in 22%, 26%, and 11% of the patients, respectively. Inconclusive test results, in which the patients failed to achieve work load at 85% MHR and showed no evidence of myocardial ischemia, were obtained in 42% of the patients. Major reasons for discontinuation of exercise tests with inconclusive results were leg fatigue (36%), general fatigue (27%), and dyspnea (12%). Of 177 hospitalized-patients, positive, negative, and equivocal test results were obtained in 63%, 15%, and 2% of the patients, respectively. Inconclusive test results were obtained in 21% of the patients. The most frequent end point of the inconclusive tests was leg fatigue(51%). In 177 hospitalized-patients, coronary arteriography revealed significant coronary artery lesions in 69% of the patients (single vessel disease: 28%, double vessel disease: 200, triple vessel disease: 21%). By correlating the results of treadmill test with findings of coronary arteriography, we found 56% true positive, 6% false positive, 11% true negative, and 4% false negative results of the tests. In 37 patients with inconclusive test results, 16 patients revealed significant coronary, artery disease. Accordingly, the sensitivity, the specificity, and the predictability were 93%, 63%, and 90% respectively.
In this study, the sensitivity and the predictability of the treadmill test were significantly high. These findings support the feasibility of the test in patients with angina pectoris. However, about half of the treadmill tests performed by out-patients resulted in inconclusive studies. This inconclusiveness may limit the clinical value of the treadmill test. It is necessary to improve the method or protocol of the treadmill exercise test. These improvements may make the treadmill test more valuable in the diagnosis of coronary artery disease.
